PRF1 and neoplasm: NK cells participate in immune regulation via a variety of mechanisms, including (1) the expression of CD16 to exert antibody-dependent cytotoxicity (ADCC) and detect target cells encapsulated in antibodies; (2) the production of perforin and granzyme to induce apoptosis in tumor cells directly; and (3) the release of antitumor cytokines such as TNF-α and IFN-γ (22).